1. Field of the Invention
This invention relates to a resettable tumbler lock, more particularly to a resettable tumbler lock having tumbler holes with cross sections that differ from each other in at least one of the group consisting of shape, size, and orientation.
2. Description of the Related Art
U.S. Pat. No. 6,550,299 discloses a conventional resettable tumbler lock that includes a housing, a first sleeve mounted rotatably in the housing and formed with a plurality of axially extending holes and a first locking hole, a second sleeve mounted in and secured to the housing and formed with a plurality of axially extending holes and a second locking hole, a cylindrical latch-connecting part disposed between and in end-to-end contact with the first and second sleeves and formed with a plurality of axially extending holes and a middle locking hole, and a plurality of spring-biased tumbler units including first tumbler pins disposed movably and respectively in the holes in the first sleeve, middle tumbler pins disposed movably and respectively in the holes in the latch-connecting part, second tumbler pins disposed movably and respectively in the holes in the second sleeve, a first locking pin disposed movably in the first locking hole, a second locking pin disposed movably in the second locking hole, and a middle locking pin disposed movably in the middle locking hole. The latch-connecting part is provided with a latch for locking purposes, and is further formed with a plurality of blind bores. Each of the tumbler units further includes a plurality of spring-biased tumbler pads that are disposed movably in each of the blind bores and optionally and selectively in a respective one of the holes in the first sleeve. A plurality of reset keys, each of which is formed with different depths of notches, are provided for the resettable tumbler lock so that the total axial length of each of the tumbler units (i.e., the total axial length of the first tumbler pin, the middle tumbler pin, the second tumbler pin, and the tumbler pad(s) which is (are) present in the respective hole in the first sleeve) in a respective one of the holes in the first sleeve, a respective one of the holes in the latch-connecting part, and a respective one of the holes in the second sleeve can be changed in accordance with a corresponding one of the depths of the notches of a respective one of the reset keys and so that the resettable tumbler lock can be locked and unlocked through an operating key corresponding to the respective reset key. To change the total axial length of any of the tumbler units, the first sleeve is first rotated relative to the latch-connecting part using a current reset key from a normal angular position to a resettable angular position, in which the holes in the first sleeve are aligned axially and respectively with the blind bores in the latch-connecting part, followed by replacing the current reset key with a desired reset key so that a predetermined number of the tumbler pads can be moved into or out of a respective hole in the first sleeve in accordance with the depths of the notches of the desired reset key. The desired reset key is then rotated from the resettable angular position to the normal angular position, and is subsequently removed therefrom. As such, the resettable tumbler lock can be locked and unlocked by co-rotating the latch-connecting part relative to the second sleeve using a corresponding operating key. The middle locking pin in the middle locking hole crosses a locking plane defined by an interface between ends of the latch-connecting part and the second sleeve when a current one of the reset keys is inserted into a keyhole in the resettable tumbler lock, thereby preventing rotation of the latch-connecting part relative to the second sleeve and permitting rotation of the first sleeve relative to the latch-connecting part. An interface between ends of the middle locking pin and the second locking pin and an interface between ends of each pair of the middle tumbler pin and the second tumbler pin lie on the locking plane when the corresponding operating key is inserted into the keyhole, thereby permitting co-rotation of the first sleeve and the latch-connecting part.
The shapes of the holes in the first sleeve are identical, are circular, and are the same as those of the holes in the latch-connecting part and the second sleeve and those of the blind bores in the latch-connecting part. The shape and size of each of the first and second tumbler pins, the middle tumbler pins, and the tumbler pads conform to those of the holes in the first and second sleeves and the latch-connecting part.
The conventional resettable tumbler lock is disadvantageous in that since the shapes of the holes in the first sleeve are circular and are identical to those of the blind bores in the latch-connecting part, an innermost tumbler pad in the respective hole in the first sleeve tends to be undesirably moved across the interface between the first sleeve and the latch-connecting part and to extend into an aligned hole in the latch-connecting part, which is aligned with the hole in the first sleeve, by the reset key during rotation of the first sleeve from the resettable angular position to the normal angular position, which results in a deadlock situation in which the first sleeve cannot be further rotated to the normal angular position by the reset key and the reset key cannot be removed from the keyhole. Moreover, since small clearances are present between moving parts, i.e., the first sleeve and the latch-connecting part and the middle tumbler pin and an adjacent one of the tumbler pads, of the resettable tumbler lock, the innermost tumbler pad in the respective hole in the first sleeve is likely to be moved across the interface between the first sleeve and the latch-connecting part and be extended into the axially aligned hole in the latch-connecting part by the reset key during rotation of the first sleeve from the second angular position to the first angular position.